Process for optophysical surface treatment of polymer substrates and device for implementing the process

ABSTRACT

A surface treatment process which enables a substrate (polymer) to be given specific physical properties, especially surface nanoporosity, for example with a view to electroless metallizing it, and which completely replaces surface treatment by sulfo-chromic pickling. The surface treatment includes a hybrid UV/corona treatment of the substrate surface followed by non-electrolytic metallization. A device for implementing these processes is also disclosed.

TECHNICAL FIELD

The technical field of the invention is that of the surface treatment ofpolymer or copolymer substrates, e.g. ABS (Acrylonitrile ButadieneStyrene), in particular for covering same with metallic films.

The present invention also relates to non-electrolytic metallizationmethods of substrates for decoration, e.g. chrome plating of automobileparts and for aeronautics. The present invention relates to thenon-electrolytic metallization of substrates for electronics, inparticular the fabrication of conductive paths.

PRIOR ART Technical Problem

In the field of non-electrolytic metallization of polymer substratessuch as ABS, a pre-treatment of the substrate surface is required tofacilitate the adherence of the metallic film.

The most common pre-treatment is a chemical surface oxidation treatmentvia sulfochromic attack, described in particular in U.S. Pat. No.3,769,061, GB-A-1240294 and GB-A-1291351. This very corrosive treatmentenables a micro-porous/nano-porous surface to be obtained to facilitatethe mechanical anchoring of the metallic film.

The sulfochromic mixture is a mixture of sulfuric acid and potassium orsodium chromate H₂S0₄/(K₂,Na₂)Cr₂O₇. This mixture is very toxic anddangerous for the environment: the chromium VI salts contained in themixture are declared by the European Union, to be category 1 and 2 humancarcinogens. In addition to the toxicity problems of the compounds used,surface treatment via sulfochromic attack does not give satisfactoryadherence results when the non-electrolytic metallization is carried outusing the Jet Metal Technologies company's methods, described inparticular in FR-A-2 763 962 and in the French patent application filedwith the number 06 10287. Indeed, because the oxidation is very deep andthe metallic film very thin, the pores created by oxidation induce aphenomenon of delamination of the metallic film with time.

Other chemical oxidations are used, less commonly. It can be the use ofother strong oxidizers such as potassium permanganate. The latter isflammable, noxious for humans and toxic for aquatic organisms.

It can also be an oxidation pre-treatment using ozone, by heating,described in particular in JP-A-1092377. In this treatment, oxidation isaccelerated by ultra-violet (UV) irradiation. Ozone is a flammable gaswhich spontaneously decomposes into molecular oxygen. It is also toxicby inhalation and corrosive.

To overcome the problems linked to the use of oxidizing chemical agentswhich are dangerous and polluting, mechanical or physical pre-treatmentsolutions have been considered.

In particular, a mechanical abrasion pre-treatment via sanding whichhas, among other characteristics, the inconvenience of being tooabrasive. Therefore, to achieve the same brilliant finish, a muchthicker metallic deposition should be performed. The costs ofmetallization are, for this reason, considerably increased.

A physical pre-treatment is also known using plasma under reducedpressure, with heating under a controlled atmosphere. Another knownphysical pre-treatment of the surface is the flaming treatment.

These two types of physical pre-treatments are not very satisfactory interms of the quality of film adherence.

OBJECTIVES

It would be desirable therefore, to have a surface treatment methodwhich confers to the polymer substrate, specific physical properties,namely surface nanoporosity, e.g. for the non-electrolytic metallizationthereof; and which would totally replace the surface treatment viasulfochromic attack.

It would be also desirable to have a non-electrolytic method formetalizing the surface of a polymer substrate, which would satisfy atleast one of the following objectives:

-   -   the method should facilitate the adherence of the metallic film        to the surface of the polymer substrate,    -   the method should make possible the deposition of as thin a        metallic film as possible, having more particularly, optical        properties, e.g. reflectivity and conductivity properties,    -   the method should be “clean”, i.e. to make the polymer surface        nano-porous prior to metallization, the method should not use        toxic, polluting and noxious solutions, like strong oxidizers,        such as sulfochromic oxidizers or potassium permanganate,    -   the method should enable the effluents coming from the process        to be recycled,    -   the method should be implemented using a compact installation        which would be integrated into the current production lines,        e.g. with a cabin length ranging between 1 m and 5 m, and making        possible, surface treatment on automated lines.

Another objective of the invention is that of providing a device for thein-line implementation of the whole treatment and metallization methodfor substrates.

BRIEF DESCRIPTION OF THE INVENTION

After long investigations, the applicant found that a combined UV/Coronatreatment of the surface of the, preferably polymer substrate tometalize, replaces perfectly the existing treatment by sulfochromicattack and, in addition, makes it possible to increase the adherence ofthe metallic film to the, preferably polymer substrate and to enhancethe decorative appearance of same.

For this reason, the object of the present invention is a surfacetreatment method for a substrate, characterized in that the methodcomprises a combined UV/Corona treatment of the, preferably polymer,substrate surface.

In the sense of the invention, the term “polymer” designates thehomo-polymers and the copolymers such as, e.g. Acrylonitrile ButadieneStyrene (ABS).

By “combined UV/Corona treatment”, it is understood e.g. that thesubstrate undergoes one or more times, a Corona electrical dischargetreatment and on or more times, a UV exposure of UV treatment. These UVand Corona treatments are simultaneous or non-simultaneous, and can beperformed in any order.

The

corona treatment

term means, e.g. that the substrate to be metalized undergoes electricaldischarges e.g. of a power of 1 to 100 kilowatts 35 (kW) with a materialintended to this effect and comprising one or more, preferably two orthree, discharge heads (or probe). In the present invention, the term“Corona treatment” should be understood in the largest sense thereof,namely including the treatment using atmospheric plasma “air plasma”,“flame plasma”, and chemical plasma.

In the sense of the present invention,

UV treatment

corresponds e.g. to the passage of the substrate to be metalizedunderneath an Ultra-Violet lamp, of which the emission spectrum is e.g.of 200 nm to 600 nm, with an energy peak at the wavelength of 365 nm,e.g. an HK 125® lamp marketed by PHILIPS®.

It is preferable that the combined UV/Corona treatment of the substratesurface occurs just prior to the metallization stage, without anintermediate step. Thus, the time interval between the combinedUV/Corona treatment and the metallization step is e.g. less than orequal to a few minutes. E.g., this time duration is less than or equalto 30 (thirty) minutes, preferably less than or equal to 5 (five)minutes and more preferably less than or equal to 1 (one) minute, oreven a few seconds.

DETAILED DESCRIPTION OF THE INVENTION Substrate:

In preferential implementation conditions for this above-describedmethod, the substrate is a polymer, preferably chosen from amongst:

-   -   I—Thermoplastics, advantageously from amongst the following        thermoplastics:    -   polyolefins: polystyrene, copolymers of styrene such as        poly(styrene-butadiene-styrene) or SBS, polypropylene,        polyethylene;    -   polyamides;    -   copolymers of acrylonitrile:        -   and of methyl acrylate;        -   and of methyl methacrylate;        -   of vinyl chloride and of styrene (SAN);        -   of butadiene and of styrene (ABS), e.g. same marketed by            BAYER® under the brand name NOVODUR®;        -   of butadiene, of styrene (ABS) and of polycarbonate PC; or    -   II—Thermosetting polymers advantageously from amongst the        following thermosetting polymers:        -   polyimides;        -   polyesters;        -   phenolic resins;        -   epoxides.

Combined UV/Corona Treatment:

The combined UV/Corona treatment is chosen from amongst the followingtreatments: an alternation of a UV treatment and a Corona treatment,simultaneous UV and Corona treatments, a treatment comprising one ormore alternation sequences and one or more sequences of simultaneous UVand Corona treatments and combinations thereof.

In the present invention, the combined UV/Corona treatment comprises atleast one alternation of a UV treatment and a Corona treatment.

When the implemented substrate is made of TABS, of PABS-PC or ofpolypropylene, the alternation is preferably a series of UV followed byCorona.

According to a notable feature of this invention, the combined UV/Coronatreatment comprises 1 to 120 times the alternation of a 0.01 second to30 (thirty) minute UV treatment and a 0.01 second to 30 (thirty) minuteCorona treatment.

Preferably, the alternation of a combined UV/Corona treatment comprises3 to 16 alternations, namely 5 to 15 alternations and even morepreferably 4 to 14 alternations; e.g. 6 or 12 alternations.

The duration of the Corona treatment during the combined Corona/UVtreatment in alternation lasts preferably 0.1 seconds to 5 (five)minutes, namely 0.5 seconds to 2 (two) minutes and even morepreferentially 1 (one) second to 1 (one) minute.

The duration of the UV treatment in the UV/Corona alternation lastspreferably 30 (thirty) seconds to 15 (fifteen) minutes, namely 1 (one)to 5 (five) minutes, and even more preferentially from 1 (one to 2 (two)minutes.

In the sense of the present invention, the duration of the Coronatreatment is e.g. the duration during which a unit of area of thesurface to be treated is exposed or undergoes a Corona discharge using aCorona device of which the probe (or discharge head) has a given area,e.g. of 10 cm², which corresponds to the unit area to be treated. Theduration of the Corona treatment can last e.g. 15 seconds for a unitarea of 10 cm² of a 100 cm² flat surface to be treated. This isequivalent to a 15 (fifteen) second total Corona treatment of thesurface, and to a 75 (seventy five) second combined UV/Corona treatment,corresponding to 60 (sixty) seconds of UV treatment and 15 seconds ofCorona treatment.

According to the method in the invention, the alternation can start andend indifferently, either by the Corona treatment or the UV treatmentduring the combined Corona/UV treatment in alternation. Preferably, itis started with the UV treatment.

The object of the present invention is also a surface treatment methodwhere the combined UV/Corona treatment as defined above is followed by anon-electrolytic metallization of the substrate treated as described.

Metallization: First Embodiment

In a first embodiment of the metallization method as described above,the non-electrolytic metallization is a non-electrolytic metallizationby the spraying of one or more redox (oxidation-reduction) solutions inthe form of aerosol(s).

-   -   Metallization by spraying of one or more redox solutions in the        form of aerosol(s) means that the non-electrolytic metallization        step comprises at least the following steps:        -   spraying of one or more redox solutions in the form of            aerosol(s),        -   rinsing.    -   In the sense of the invention, “one or more redox solutions        means e.g.:        -   either a single solution containing at the same time a            plurality of oxidizers and one or more reducers        -   or two solutions: the first solution containing one or more            oxidizers and the second one or more reducers,        -   or a plurality of solutions, each containing either one or            more oxidizers or one or more reducers, with the condition            that there is at least one oxidizing solution and one            reducing solution.    -   According to a first possibility, non-electrolytic metallization        by spraying of one or more redox solutions in the form of        aerosol(s) comprises, in this order, the following steps:        -   wetting the surface,        -   spraying of one or more redox solutions in the form of            aerosol(s),        -   rinsing.    -   According to a second possibility, non-electrolytic        metallization by spraying of one or more redox solutions in the        form of aerosol(s) comprises, in this order, the following        steps:        -   sensitizing the surface, preferably with a SnCl₂ solution,        -   rinsing,        -   spraying of one or more redox solutions in the form of            aerosol(s),        -   rinsing.

Spraying:

The redox solution used during non-electrolytic metallization aresprayed in the form of aerosol(s) over the substrate and are preferablyobtained from solutions, advantageously aqueous, of one or moreoxidizing metallic cations and one or more reducing compounds. Theseredox solutions are preferably obtained by dilution of concentratedstock solutions. The diluent is preferably water.

It follows that according to a preferred arrangement of the invention,the spraying aerosol(s) is/are produced by the nebulizing and/oratomizing of solution(s) and/or dispersion(s) to obtain a fog ofdroplets smaller than 100 micrometers, preferably 60 micrometers andeven more preferably 0.1 to 50 micrometers.

In the method according to the invention, the spraying of metallicsolutions preferably takes place continuously and the substrate isdriven into movement and undergoes spraying. E.g., when the metallicdeposit is made from silver, the spraying is continuous. For a metallicdeposit made e.g. from nickel, the spraying is carried out inalternation with relaxation times.

In the method of the invention, the sprayings lasts e.g. 0.5 to 1000seconds, preferably from 1 (one) to 800 seconds and even more preferably2 (two) to 600 seconds for a 1 dm² area to be metalized. The substratecan be driven into at least partial rotation during the spraying of themetallization.

According to a first method of spraying, one or more metallic cationicsolutions and one or more reducing solutions are continuously andsimultaneously sprayed, in one or more aerosols, over the surface to betreated. In this case, the mixture between the oxidizing solution andthe reducing solution can be made just prior to the formation of theaerosol to be sprayed or by fusion between an aerosol produced from theoxidizing solution and an aerosol produced from the reducing solution,preferably prior to entering into contact with the surface of thesubstrate to be metalized.

According to a second spraying method, one or more metallic cationicsolutions, then one or more reducing solutions are successively sprayed,by intermediary of one or more aerosols. In other terms, the spraying ofthe redox solution is carried out by the separate spraying of one ormore solutions of one or more metallic oxidizers and one or moresolutions of one or more reducers. This second possibility correspondsto an alternate spraying of the reducing solution or solutions and ofthe metallic salt or salts.

In the frame of the second spraying method, the association of aplurality of oxidizing metallic cations to form a multilayer ofdifferent metals or alloys is such that the different salts are,preferably, naturally sprayed separately from the reducer, but alsoseparately one from the others, and successively. It is obvious that, inaddition to the different nature of the metallic cations, usingdifferent counter-anions can be considered.

According to a variant of the spraying step, a metastable mixture of theoxidizer(s) and the reducer(s) is produced, and after having sprayed themixture, the latter is activated, so that the transformation into metalis initiated, preferably by bringing into contact with an initiator,advantageously brought by intermediary of one or more aerosols, priorto, during or following the spraying of the reaction mixture. Thisvariant enables the oxidizer and the reducer to pre-mix while delayingthe reaction thereof until same carpet the substrate after spraying. Theinitiation or activation of the reaction is then obtained by anyphysical (temperature, UV, etc.) or chemical means.

Beyond the methodological considerations presented above and illustratedhereafter by examples, it is appropriate to give some preciseinformation about the products implemented in the method according tothe invention.

Water appears to be the most suitable solvent, without however,excluding the possibility of using organic solvents, to producesolutions from which the sprayed aerosols are going to be produced.

The redox solutions sprayed during the metallization step of thesubstrate are one or more solutions of a metallic oxidizer and one ormore solutions of a reducer.

The concentrations of metallic salts in the oxidizing solution to besprayed are of 0.1 g/l to 100 g/l and preferably from 1 (one) to 60 g/l,and the concentrations of metallic salts of the stock solutions are from0.5 g/l to 10³ g/l, or the dilution factor of the stock solutions isfrom 5 to 500. Advantageously, the metallic salts are chosen fromamongst the following compounds: silver nitrate, nickel sulfate, coppersulfate, tin chloride, and mixtures thereof.

The selection of reducers is preferably made from amongst the followingcompounds: borohydride, di-methyl-amino-borane, hydrazine, sodiumhypophosphite, formaldehyde, lithium aluminum hydride, reducing sugarssuch as glucose and sodium erythorbate, and mixtures thereof. Theselection of the reducer imposes taking into account the pH and thetargeted properties of xc the metallization film. These routineadjustments can be done by a person skilled in the art. Theconcentrations of reducer in the reducing solution to be sprayed arefrom 0.1 g/l to 100 g/l and preferably from 1 (one) to 60 g/l, and theconcentrations of reducer in the stock solutions are from 0.5 g/l to 10³g/l, or the dilution factor of the stock solution is from 5 to 100.

According to a special arrangement of the invention, particles areincorporated into at least one of the redox solutions, to be sprayed atthe time of metallization. The particles are thus trapped in themetallic deposit. These hard particles are e.g. diamond, ceramics,carbon nanotubes, metallic particles, rare earths oxides,polytetratluoroethylene (PTFE), graphite, metallic oxides and mixturesthereof. The incorporation of these particles into the metallic filmyields special mechanical and esthetical properties to the metallicsubstrate.

Rinsing:

Advantageously, the rinsing step, i.e. bringing into contact the entiresurface or part of the surface with one or more sources of rinsingliquid, is carried out by spraying a rinsing liquid aerosol, preferablywater.

Wetting:

The wetting prior step mentioned above consists of covering the surfaceof the substrate with a liquid film. The choice of the wetting liquid ismade from within the following group: deionized water or non-deionizedwater, with the possible addition of one or more anionic, cationic orneutral surfactants, an alcoholic solution comprising one or morealcohols (e.g. isopropyl alcohol, ethanol) and mixtures thereof. Inparticular, deionized water with an addition of an anionic surfactantand ethanol is chosen as the wetting liquid. In a wetting variantaccording to which the wetting liquid is transformed into vapor which issprayed over the substrate on which same condenses, it is preferablethat the liquid is essentially aqueous for obvious reasons of industrialconvenience. The duration of the wetting depends upon the area of theconsidered substrate and of the flow rate of the spraying of the wettingaerosol.

Sensitization:

According to a special embodiment of the invention, the sensitizationstep for the surface of the substrate can be implemented by means of asensitization solution, particularly stannous chloride, e.g. accordingto the implementation mode described in FR-A-2 763 962. In this case, arinsing step using a rinsing liquid such as described above, is carriedout immediately following the sensitization step, without anintermediate step.

Thermal Treatment:

According to this first embodiment, the metalized substrate can undergoa thermal treatment just following the rinsing step which follows thespraying step, to reinforce adherence.

The thermal treatment preferably takes place in an infrared oven ortunnel at a temperature from 50° C. to 150° C., more preferably from 60°C. to 120° C. and even more preferably of about 100° C., for a durationof 5 minutes to 3 hours, preferably between 15 minutes and 90 minutes,and more preferably of about 60 minutes. The thermal treatment can alsobe a drying step which consists of draining the rinsing water. It can beadvantageously carried out at a temperature between 20° C. and 40° C.using e.g. a system of pulsed compressed air at 5 bar/pulse at atemperature of 20° C. to 40° C.

All the embodiments of the non-electrolytic metallization step byspraying one or more redox solutions in the form of aerosol(s) in thesense of the invention, are more precisely described in FR-A-2 763 962and the application for a French patent filed under the number 06 10287.

Second Embodiment

According to a second embodiment of the metallization method asdescribed above, the non-electrolytic metallization is anon-electrolytic metallization by immersion in one or more bathscontaining one or more redox solutions. This method is called “chemicalmetallization” by a person skilled in the art.

Non-electrolytic metallization by immersion in one or more bathscontaining one or more redox solutions means that the non-electrolyticmetallization comprises, in this order, at least the following steps:

-   -   sensitization of the surface, preferably using a SnCl₂ solution,    -   activation of the surface, preferably using a PdCl₂ solution,    -   rinsing with hydrochloric acid or caustic soda,    -   immersion of the substrate in one or more baths of redox        solutions,    -   rinsing.

Preferably, the parts to be treated are immersed in a bath mainlycontaining three agents: a metallic salt, a reducer and a complexingagent which prevents the spontaneous reduction and the precipitation ofthe bath.

All the embodiments of the non-electrolytic metallization step byimmersion in one or more baths containing one or more redox solutions inthe sense of the invention are more specifically described in FR 2 719839.

According to a preferred embodiment of the method, the metallic depositproduced is a chemical nickel deposit. E.g., ATOTECH® chemical and redoxsolutions can be used for such a deposit:

-   -   for the activation, FUTURON® solutions can be used,    -   NOVIGANTH AK® solutions can be used for chemical nickel        metallization.

Finishing Layer:

According to a special embodiment of the invention, the methodcomprises, in addition to and following the non-electrolyticmetallization step, a step for producing a finishing layer.

The step of producing a finishing layer is preferably the production ofan electrolytic thickening of the metalized surface. The electrolyticthickening is preferably achieved by immersing the substrate, which isat least partially metalized, in a solution bath containing electrolytesand, by passing a sufficiently high electric current between theexisting electrode in the electrolytic bath and the substrate which isat least partially metalized. In the framework of the invention, theelectrolytes are metallic ions suitable for being deposited onto themetalized surface of the substrate, e.g. chosen amongst the ions of thefollowing metals: chrome, nickel, silver or copper, such as Cr⁶⁺, Ni²⁺,Ag⁺ and Cu²⁺. A stacking of a plurality of metallic layers produced bysuccessive steps can occur, such as a thickening of copper followed by alayer of nickel and a final layer of chromium. The technique ofelectrolytic thickening is well known to a person skilled in the art.E.g, the quantity of current required to produce a 1 micrometer copperlayer on a substrate having a metalized area of 1 dm² is 0.5 to 20 Afrom a solution of Cu²⁺ ions at 250 g/l. Generally, the thickness of thefinishing layer produced by electrolytic thickening is from 2 to 40micrometers. When the finishing layer is produced by electrolyticthickening, the substrate is preferably partially metalized. Partialmetallization is possible namely by masking part of the surface of thesubstrate prior to metallization.

In the metallization method according to the invention, and preferablyin the first embodiment of the metallization, the effluents coming fromthe different steps of the method are advantageously retreated andrecycled to be used in the method, and to limit the ecological impact.

In the metallization method as described above and according to thefirst embodiment, the retreatment and the recycling of the effluentscomprise, in this order, the following steps/

-   -   recuperation of the effluents, particularly from dirty water, in        a container,    -   possible addition of a flocculent,    -   possible decantation,    -   possible separation of the filtrate and sludge, namely by        filtration,    -   possible neutralization of the filtrate, in particular the        removal of ammonia, by addition of acid while controlling the        pH,    -   distillation of the filtrate, preferably in an evaporator,    -   possible passage over a system of activated carbon,    -   reuse of the distillate, e.g. in a metallization method as        rinsing water or as diluent of the redox stock solutions or        disposal into the sewer.

The flocculent added to the effluents is preferably a charged organicpolymer, such as same marketed by SNF FLOERGER®.

The separation of the supernatant and the sludge is advantageouslyachieved by filtration on sintered filters or by overflowing.

The sludge can then be disposed of and directed towards a specializedcentre for retreating or reusing waste.

The obtained filtrate can be neutralized, in particular by adding anacid solution with a normality of 0.1 to 10 N until the filtrate reachesa pH of 5 to 6. The acids used for neutralizing in particular theammonia existing in the filtrate are chosen amongst hydrochloric acid,sulfuric acid, nitric acid and mixtures thereof.

The distillation of the filtrate is preferably achieved using anevaporator, and the filtrate is heated at a temperature of 90 to 120° C.The residue which remains at the bottom of the boiler at the end of thedistillation is disposed of and sent to a specialized center forretreating or reusing waste. The distilled water can be reused in themetallization method, and in particular for the dilution of stocksolutions and for the rinsing and wetting steps.

The advantages of the method according to the invention are numerous.The surface treatment makes possible the control of the metallizationreaction and improvement of the adherence of the metallic film to thesurface. No chemical product is used for the combined UV/Coronatreatment. Moreover, the effluents of the metallization, discharged bythe process and which are, on an industrial scale, more than one ton perday, are retreated and reused by the process. The distilled water whichcomes out of the retreatment module is pure and can be used as such forthe dilution of the oxidizer and reducer stock solutions, and forrinsing and wetting. This advantage is non-negligible from an economicalpoint of view because water consumption is considerably reduced, andfrom an ecological point of view because the quantity of waste to bedisposed of is considerably reduced. It is important to note thatindustrial water cannot be used by the method, and that a purificationstep would be required if the method would not have a module forretreating effluents and purifying dirty water. In addition, the methoduses concentrated stock solutions which are diluted on-site prior tometallization. The volume of stock solutions is therefore smaller thanif the solutions would be already diluted, which reduces costs, inparticular for transportation.

In addition, the quantities of reducer which are used are lower than theauthorized standard (ISO 14001), this compound being toxic for theenvironment, so reducing the quantities used is an important ecologicaladvantage.

In addition, the electrolytic thickening which can be produced has theadvantage of being selective: same only takes places on the metalizedsurface of the substrate, which enables embossed patterns to be created,such as conductive paths.

The object of the present application is also a method for treatingsurfaces including a combined UV/Corona treatment and a metallization ofsubstrates, as defined in the above description, where a plurality ofsubstrates are treated in line without breaking the chain. Inparticular, the method does not require any handling performed by man,with the exception of the steps of loading the substrate to be metalizedand unloading the metalized substrate.

The method described above is advantageously implemented using aindustrial metallization device which comprises the following elements:

-   -   at least one module for combined UV/Corona surface treatment,    -   at least one module for non-electrolytic metallization.

According to a preferred embodiment of the invention, the industrialdevice for the implementation of the method described above comprises,in addition, the following elements:

-   -   at least one module for producing a finishing layer,    -   at least one module for retreating and recycling effluents.

The module for combined UV/Corona surface treatment comprises one ormore Corona discharge heads and one or more UV lamps. It can be, e.g. aCorona discharge tunnel marketed by the DMG® company under the name C22®and a reference UV lamp HK125® from the brand PHILIPS®.

The non electrolytic metallization module comprises means ofnon-electrolytic metallization which are the current means of sprayingsolutions, in particular same described as in FR-A-2 763 962, or meansof immersion such as electroplating lines via baths.

The means of spraying comprise, e.g. a set of HVLP (High Volume LowPressure) spray guns, said guns being each linked to one or more pumpssupplied with a solution. A first pump/gun system is provided for thewetting step. A second pump/gun system is provided for the sensitizationstep and a third for the rinsing. The spraying of metallic oxidizer andreducer solutions is carried out using at least two pump/gun systems: asystem for the oxidizer solution, and a system for the reducer solution.For spraying the oxidizing solution, the number of guns is between 1 and30, linked to at least one pump. The same applies to the spraying of thereducer solution which counts 1 to 30 guns. A final pump/gun system isprovided for rinsing following the spraying of metallization solutions.

The means of immersion are, e.g. containers (tanks or vats) in whichliquid solutions are put. The lines which are used are e.g. of the typemarketed by the CORELEC® company. The non-electrolytic metallizationmodule can also include means of thermal treatment for the metallicfilm, e.g. using an IR oven or tunnel, or a system of pulsed compressedair at 5 bar/air pulsed at a temperature comprised between 20 and 40° C.

The module for producing a finishing layer comprises means of producingan electrolytic thickening of the metalized surface, particularly anelectrolytic bath filled with solution containing electrolytes, at leastone electrode and a device for the circulation of an electric current.

When the device according to the invention uses means ofnon-electrolytic metallization which are current means of sprayingsolutions, then the device can be, in addition, equipped with a modulefor retreating and recycling effluents.

This module for retreating and recycling effluents comprises means ofrecuperating effluents, which are, e.g. recuperation channels, such aschicane screens which direct the effluents towards a recuperationcontainer, and which are intended to protect the mechanism of theconveyer on which are arranged the substrates to be metalized.

This module for retreating and recycling effluents also comprises:

-   -   means of decantation and separation of the filtrate and the        sludge, e.g. a decanter or a overflow device,    -   means of distillation, e.g. using an installation comprising one        or more boilers and one or more refrigerated columns.

When the effluents are retreated, the purified water is directed, viameans of conveying liquids, e.g. pipes and pumps, towards the differentmodules of the method, to be reused.

According to a preferred embodiment of the device of the invention, thesubstrates to be metalized are placed on a means of moving thesubstrates from one module to another. It can be, e.g. a conveyer,particularly a belt and pin conveyer, when a metallization module isused, which comprises means of spraying. It can be, e.g. a swing traywhenever the metallization module consists of means of immersion.

Preferably, the means of moving the substrates is equipped with means ofdriving into rotation the substrates about the axes thereof.

The present invention also relates to a metalized substrate obtainedusing the method as described above, the substrate being in particularan automobile part or a part used in aeronautics.

The present invention also has as object, a metalized substrate obtainedusing the method as previously described, the substrate being inparticular a part used in electronics such as a conductive path or aradio frequency identification (RFID) antenna.

The invention will be better understood when reading the followingdescription of examples of implementation of the method and embodimentsof the device, in reference to the appended drawings where:

FIG. 1 shows a global diagram of the embodiment of the metallizationmethod according to the invention,

FIG. 2 shows a diagram of a device according to the invention,

FIG. 3 shows a transverse cross-section of a substrate metalized usingthe method according to the invention.

FIG. 4 shows a transverse cross-section of a substrate metalized usingthe method according to the invention.

In FIG. 1 a summary diagram of the essential and optional steps of theembodiment of the metallization method according to the invention, isshown.

FIG. 2 is a schematic representation of a device for embodying a methodaccording to the invention.

This device comprises the following three modules:

-   -   a combined UV/Corona treatment module 3,    -   a non-electrolytic metallization module 6,    -   an optional module for producing a finishing layer 16.

The combined UV/Corona treatment module 3 comprises a UV treatment cabin4 and a Corona treatment cabin 5.

The non-electrolytic metallization module 6 comprises a spraying zone 7equipped with guns 8 linked to pumps 9, each pump being linked to itsown solution vat. Pump 10 is reserved for wetting the surface. Pump 11is provided for the step of sensitizing the surface of the substrate andpump 12 for rinsing. Pumps 13 and 14 are pumps linked to redoxsolutions. Pump 15 is a rinsing pump.

The optional module for producing a finishing layer 16 is a cabin forelectrolytic thickening consisting of a container containing anelectrolytic solution 17 and electrodes 18 and 19 in between whichcirculates a sufficiently high current for producing electrolyticthickening. Electrode 18 plunges into the electrolytic solution bath andelectrode 19 is linked to the metalized substrate.

During a process using this device, the substrate to metalize 1 isplaced on a swing tray 2 which conveys same towards the combinedUV/Corona treatment module 3 where same undergoes a combined UV/Coronatreatment via the UV treatment cabin 4 and Corona treatment cabin 5. Atthis stage, the swing tray 2 makes round trips between the treatmentcabins UV′ and Corona 5, in alternation.

The substrate which is treated is then conveyed towards thenon-electrolytic metallization module 6 installed after the combinedUV/Corona treatment module 3. In the spraying zone 7, pump 10 wets thesurface, e.g. with water. Then pump 11 sprays a solution of stannouschloride. This sensitization is followed by a rinsing step, e.g. withwater, using pump 12. Pumps 13 and 14 then spray the redox solutionsrequired for the production of the metallic film. Pump 13 is e.g. linkedto the solution of metallic ions and pump 14 is linked to the reducersolution. The actuation of these pumps can be simultaneous orconsecutive. Following the metallization, a rinsing step is providedusing pump 15 linked to a solution of rinsing liquid, e.g. water.

The substrate thus metalized is finally conveyed towards the optionalmodule for producing a finishing layer 16 where the substrate undergoeselectrolytic thickening. The substrate is plunged into the electrolyticsolution bath, electrode 18 is plunged into the electrolytic solutionbath, electrode 19 is attached to the substrate to be metalized and acurrent is circulated between the two electrodes.

The substrate 20 which has been metalized using the method according tothe invention can then be unloaded after the production of the finishinglayer.

FIGS. 3 and 4 each show a schematic transverse cross-section of asubstrate metalized by an embodiment of the method of the invention.

In FIG. 3, the metalized substrate consists of three layers A, B and C.Layer A stands for the substrate, e.g. a substrate made of ABS, layer Bis the metallic film, e.g. a chromium film, and layer C is the result ofelectrolytic thickening in a bath containing nickel sulfate.

In FIG. 4, the metalized substrate also consists of three layers calledA′, B′ and C′. A′ is a substrate, e.g. an ABS-PC. Layer B′ is a metalliclayer, e.g. made of nickel, obtained via metallization with masking partof the surface. Layer C′ is a copper layer, which is the result ofelectrolytic thickening in a bath containing copper sulfate. Thedeposition of this layer C′ is selective and only takes place on thesurface of the layer B′.

EXAMPLES Example 1 Chromium Metallization of an ABS Substrate

A shaped part made of ABS NOVODUR® from BAYER®, on the order of 10 cm inlength, 10 cm in width and 1 cm in thickness, is driven into rotation ona rotating plate at 0.5 rpm. The rotating part is then treated using analternating UV/Corona treatment according to the following conditions:

-   -   1 minute under a UV HK125® (125 mW) lamp from PHILIPS® having an        emission spectrum with a wavelength of 200-600 nm (peak at 365        nm),    -   1 minute Corona discharge at 32 kW with a C22® apparatus from        DMG® distributed over the whole surface. The probe of the        apparatus is equipped with two electrodes and a surface area of        10 cm². So every 10 cm² of the part undergoes a Corona discharge        for 1.6 seconds. The probe is placed at 10 mm from the surface        and the scan of the whole surface in 1 (one) minute,    -   this alternation is repeated 6 times.    -   The part which has been treated is placed inside a module for        non-electrolytic metallization using spraying, where same        successively undergoes:        -   wetting by water spraying for 5 seconds,        -   spraying of an aqueous solution of nickel salt (MSO4) with a            concentration of 7 g/l simultaneously with spraying of an            aqueous solution of sodium borohydride at 10 g/l for 600            seconds in alternation with relaxation times,        -   water rinsing for 10 seconds.

An ABS part is thus obtained, with a metallic primary layer made ofelectrically conductive nickel on which a finishing range is producedusing electrolytic thickening according to a protocol and using amaterial and products known per se. This thickening consists of thefollowing successive layers: copper (20 microns)+nickel (5microns)+chromium (0.5 microns).

The ABS part with a Ni metallic primary is therefore successivelyimmersed:

-   -   in an electrolytic solution bath of copper ions, marketed as        CUPRACIDE ULTRA® from the ATOTECH® company (current 2 A, 700 s),    -   in an electrolytic solution bath of nickel ions, marketed as        NiMAC® by the company MACDERMID® (current 2 A, 150 s),    -   then in an electrolytic solution bath of chromium ions marketed        as the MACRO ME 8210-CHROME® range by the company MACDERMID®,        with a current intensity sufficiently high and a duration long        enough to obtain a layer of 0.5 micrometers.

Example 2 Metallization with Nickel of a Part Made of ABS-PC

An ABS-PC part from BAYER®, 10 cm long by 10 cm wide and 1 cm thick, andon which part of the surface is masked in order to produce a printedcircuit pattern, is driven into rotation on a rotating plate at 5 rpm.The rotating part is then treated using an alternating UV/Coronatreatment according to the following conditions:

-   -   2 minutes under a UV HK125® (125 mW) lamp from PHILIPS® having        an emission spectrum with a wavelength of 200-600 nm (peak at        365 nm)    -   1 minute Corona discharge at 32 Volts with a C22® apparatus from        DMG® over the whole surface. The probe of the apparatus is        equipped with two electrodes. The probe is placed at 10 mm from        the surface.    -   This alternation is repeated 12 times.    -   The part which has been treated is placed inside a module for        non-electrolytic metallization where same successively        undergoes:        -   a sensitization of the surface by spraying a stannous            chloride for 5 seconds,        -   rinsing the sensitization solution by water spraying for 10            seconds,        -   spraying an aqueous solution of ammonium silver nitrate of a            concentration of 3 g/l simultaneously with spraying an            aqueous solution of glucose at 10 g/l for 30 seconds,        -   water rinsing for 25 seconds.

The mask is removed from a part of the surface.

The part is thus partially metalized and immersed in an electrolyticsolution bath of copper ions, marketed as CUPRACIDE ULTRA® by thecompany ATOTECH®. An electrode is placed in the bath and a 2 A currentis applied between the electrode and the substrate. The duration of theelectrolysis is 700 seconds and thickening is of 20 microns.

A metalized and copper-thickened ABS-PC part is thus obtained.

A standardized Peel Test ASTM B533 is run on this part. A mean value of0.7 N/mm is obtained.

Example 3 Primary Metallization with Copper of a Part Made of ABS

A part of ABS of the NOVODUR® range from BAYER®, 10 cm long by 10 cmwide and 1 cm thick, and of which part of the surface is masked in orderto produce a printed circuit pattern, is driven into rotation on arotating plate at 5 rpm. The rotating part is then treated using analternating UV/Corona treatment according to the following conditions:

-   -   2.5 minutes under a UV HK125® (125 mW) lamp from PHILIPS® having        an emission spectrum with a wavelength of 200-600 nm (peak at        365 nm)    -   2 minute Corona discharge at 32 Volts with a C22® apparatus from        DMG® over the whole surface. The probe of the apparatus is        equipped with two electrodes. The probe is placed at 10 mm from        the surface.    -   This alternation is repeated 12 times.    -   The part which has been treated is placed inside a module for        non-electrolytic metallization where same successively        undergoes:    -   activation using colloidal palladium of the FUTURON® range from        ATOTECH® for 7 minutes,    -   water rinsing for 25 seconds,    -   metallization by chemical bath of nickel of the NOVOGANTH AK®        range from ATOTECH® for 15 minutes,    -   rinsing in a water bath for 30 seconds.

The part which has been metalized (under a nickel layer) is immersed inan electrolytic solution bath of copper ions at 250 g/l. An electrode isplaced inside the bath and a 2 A current is applied between theelectrode and the substrate. The duration of the electrolysis is of 700seconds and thickening is of 20 microns. The range is completed by anelectrolytic deposit of nickel of 5 microns and a chromium layer of 0.5microns. This copper/nickel thickening is carried out in the same way asin example 1.

A chromium-metalized ABS part is thus obtained for applications in theautomobile field, in particular.

A standardized Peel Test ASTM B533 is run on the part which wasobtained. A mean value of 0.75 N/mm is obtained.

1. Method for treating a substrate surface comprising a combinedUV/Corona treatment of the substrate surface followed by anon-electrolytic metallization of the substrate which has been treated.2. Method for surface treatment according to claim 1, wherein thecombined UV/Corona treatment is chosen from the group consisting of analternation of a UV treatment and a Corona treatment, a simultaneity ofUV and Corona treatments, a treatment comprising one or more alternationsequences and one or more simultaneous sequences of UV and Coronatreatments and combinations thereof.
 3. Method for surface treatmentaccording to claim 1, wherein the substrate is a polymer, preferablychosen amongst: I—Thermoplastics, advantageously amongst the followingthermoplastics: polyolefins: polystyrene, copolymers of styrene such aspoly(styrene-butadiene-styrene) or SBS, polypropylene, polyethylene;polyamides; copolymers of acrylonitrile: and of methyl acrylate; and ofmethyl methacrylate; of vinyl chloride and of styrene (SAN); ofbutadiene and of styrene (ABS); of butadiene, of styrene (ABS) and ofpolycarbonate PC; or II—Thermosetting polymers advantageously fromamongst the following thermosetting polymers: polyimides; polyesters;phenolic resins; epoxides.
 4. Method for surface treatment according toclaim 1, wherein the combined UV/Corona treatment comprises at least onealternation of a UV treatment and a Corona treatment.
 5. Method forsurface treatment according to claim 1, wherein the combined UV/Coronatreatment comprises 1 (one) to 120 times the alternation of a 0.01second to 30 minute UV treatment with a 0.01 second to 30 minute Coronatreatment.
 6. Method for surface treatment claim 1, wherein thenon-electrolytic metallization is a non-electrolytic metallization byspraying of one or more redox solutions in the form of aerosol(s). 7.Method for surface treatment according to claim 1, wherein thenon-electrolytic metallization is a non-electrolytic metallization byimmersion of the substrate in one or more baths of redox solutions. 8.Method for surface treatment according to claim 1, wherein the effluentsare retreated and recycled and wherein the retreatment and the recyclingof the effluents comprise, in this order, the following steps:recuperation of the effluents in a container, distillation in anevaporator, use of the distillate in the method for metallization ordisposal to the sewer.
 9. Method for surface treatment according toclaim 1, wherein a plurality of substrates are treated in line withoutbreaking the chain.
 10. Device for the implementation of the method asdescribed in claim 1, comprising the following elements: at least onemodule for a combined UV/Corona surface treatment, at least onemetallization module.